Optimal beam pattern to maximize inclusion residence time in an electron beam melting hearth

Abstract

Approximate probabilities of inclusion survival through an electron beam melting hearth are coniputed from nitride dissolution rates, flotation velocities, and residence times. Dissolution rates were determined by measuring shrinkage rates of pure TiN and nitrided sponge in siiiall pools of inolten titanium in an electron beam melting hearth. Flotation velocities were calculated wing correlations for fluid flow around spheres, and show that particles sink or float unless their densities ark extremely close to that of molten titanium. Flow field characteristics which lead to effective inclusion removal are discussed in terms of lieat flux pattern required to produce them, based on the electron beam's unique ability to impart a nearly arbitrary heat flux pattern to the melt surface. 'This work perforrned at Saiidia Natiortal Laboratories is supported by the U.S.

Reducing defects in remelting processes for high-performance alloys

“…3 Particle-dissolution rates have been measured by several direct approaches. 12,13 Dissolution experiments by the SMPC have been conducted in the EB furnace at Sandia's Liquid Metal Processing Laboratory. Samples were either pure, fully dense titanium nitride or Timetnitrided sponge (average 15 wt.% nitrogen).…”

“…Using these experimental values, sur-vival of nitride particles in titanium has been modeled by Powell et al 12 as a function of particle density and diameter. The model assumes spherical shape and calculates terminal floating or sinking rates based on a balance of drag force with buoyancy force for the moving particle.…”

An examination of the factors influencing the melting of solid titanium in liquid titanium

“…In another study on HDIs, Yamanaka and Ichihashi [6] investigated the dissolution of tungsten, tantalum and vanadium particles in a molten pool by utilizing a Vacuum Arc Remelting (VAR) furnace. For HIDs, Powell et al [7] investigated the dissolution of a TiN rod in liquid titanium. The dissolution rate was found to obey a linear correlation with time of 0.16 mm/min under the experimental conditions in his study.…”

The use of defects and compositional variations to elucidate physical phenomena in electron beam melted Ti-6Al-4V across scan strategies

“…Many manufacturers compensate for the known evaporation properties of high vapor pressure elements by increasing the quantity of these elements in the feedstock material, ensuring the final composition, despite element loss, is as desired [143]. Preferential vaporization is also used to remove impurity elements, such as oxygen in titanium alloys, as well as inclusions [144].…”

“…In addition to the vaporization of elements during high-temperature manufacturing processes, there are other processes which rely on the vaporization of molten metals, such as electron beam physical vapor deposition and other similar techniques [144]. While these techniques do not generally rely on preferential vaporization of select elements from feedstock material, they can be used to elucidate vaporization processes in general, particularly for metals and alloys.…”